Every gardener knows the advantages of adding compost to improve their soil, but did you know it's possible to extract the benefits of compost and apply the goodness in an easy-to-use liquid form, known as compost tea?

Earlier this year I visited Ed Ikin, Head Gardener at Nymans in West Sussex. He extolled the virtues of compost tea, which is brewed up once a week during the growing season and applied to plants in open beds as well as sprayed over hedges and lawns.

It's not exactly a new idea: commercial growers, especially organic ones, have been producing and using compost tea for years. But it hasn't really taken off with amateur gardeners, until now: Gardeners' World featured compost tea last month.

Put simply, compost tea is compost steeped in aerated water with some extra natural additives thrown in. When applied, it improves soil biology and soil structure by boosting or replenishing beneficial micro-organisms, including certain bacteria, fungi and nematodes. It can help to protect plants from diseases as well as improve the nutrient uptake – this in turn improves the health and growth of plants.

What could this be doing for your garden? Compost tea in production at Nymans. Photograph: Ed Ikin

At Laverstoke Park, an organic and biodynamic farm in Hampshire, they take their compost tea very seriously indeed. They make their own tea brewers, run seminars on the subject for commercial growers and count it as a vital part of their arsenal against plant diseases and as a way of putting natural goodness back into the soil. Their resident compost tea expert Dr Vinodh Krishnamurthy says the key to producing quality tea is to use good compost. A handy indicator for home gardeners is smell: good compost should be earthy and not unpleasant. The compost is put in a bag (similar to a large tea bag), then placed in a brewing vessel of water. The right conditions then need to be maintained during brewing to ensure the beneficial microbes multiply. It's important that the tea is also aerobic to promote the friendly bacteria – the brew needs to be aerated during the brewing process. "Food" (eg seaweed extracts, fish hydrolysate, humic acid) is usually added to the brew to feed the micro-organisms and encourage them to multiply.

Compost tea should be used straight away once it is ready, either directly to the soil from a watering can or as a foliar spray. A dilution rate of 1:1 is usual (1:5 at most), but it can also be applied undiluted without causing harm. Dr Krishnamurthy recommends not applying compost tea on leafy salad crops – at least not for 2-3 weeks before harvesting – as you can never be completely sure what is in the tea. However, it is excellent for edibles generally – for example using it on fruit trees to help prevent disease. At Laverstoke Park compost tea is sprayed from April to October. This happens once every two weeks on the vineyard, hops and apple orchard, unless they see signs of mildew when they will spray every week. Their grassland is sprayed with one or two applications a year.

If you do decide to have a go at brewing compost tea it's always a good idea to buy a professional brewing kit. The smallest models cost around £450 and will make enough compost tea to cover an acre of land. If you only have a small garden or if you have an allotment, then it's worth considering clubbing together with your local horticultural or allotment society to share the cost and the tea.

Dr Krishnamurthy describes brewing compost tea as both an art and a science. It's certainly not a quick fix, but rather a long-term fertility-building exercise. Now that amateur gardeners are increasingly interested in organic and natural ways of growing, perhaps its time has come.